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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        var n = 3234 ;

        // var h = n / 3600 ;
        // h = Math.floor(h) ;

        // 对一个小数取整
        var h = Math.floor(n / 3600) ;

        // var m = n % 3600 / 60 ;
        // m = Math.floor(m) ;
        var m = Math.floor(n % 3600 / 60) ;



        var min = 20 ;
        var max = 80 ;
        var n = Math.floor(Math.random() * (max - min) + min) ;

    </script>
</body>
</html>